[PATCH] Allow mem=mmap to also use a file backing

[fio.git] / HOWTO

diff --git a/HOWTO b/HOWTO
index 3b270b1d723460110607b1c2b455d61f35164d06..19182019f7020389e6e5e48391e8f2b6f58b5871 100644 (file)
--- a/HOWTO
+++ b/HOWTO
@@ -359,8 +359,10 @@ mem=str            Fio can use various types of memory as the io unit buffer.
 
                        shmhuge Same as shm, but use huge pages as backing.
 
-                       mmap    Use anonymous memory maps as the buffers.
-                               Allocated through mmap(2).
+                       mmap    Use mmap to allocate buffers. May either be
+                               anonymous memory, or can be file backed if
+                               a filename is given after the option. The
+                               format is mem=mmap:/path/to/file.
 
                        mmaphuge Use a memory mapped huge file as the buffer
                                backing. Append filename after mmaphuge, ala
@@ -387,6 +389,9 @@ mem=str             Fio can use various types of memory as the io unit buffer.
 hugepage-size=siint
                Defines the size of a huge page. Must at least be equal
                to the system setting, see /proc/meminfo. Defaults to 4MiB.
+               Should probably always be a multiple of megabytes, so using
+               hugepage-size=Xm is the preferred way to set this to avoid
+               setting a non-pow-2 bad value.
 
 exitall                When one job finishes, terminate the rest. The default is
                to wait for each job to finish, sometimes that is not the